Large, for instance, deep-drawn wells in car bodies, especially motor vehicles, such as, for example, trunk wells and spare-tire wells but also oil pans, have to have sufficient bottom stiffness and strength so that, first of all, they can withstand the stresses caused by the rated loads as well as by excessive loads and, secondly, they can shift natural vibrations of the bottom to a sufficiently high frequency range above a dominant excitation source, thus preventing resonances.
In order to meet these requirements, it has been a long-known procedure to reinforce such wells by means of profiled supports or so-called star-shaped supports, but this approach is associated with high costs and especially also with greater weight, as a consequence of which it runs counter to the lightweight construction envisaged by automotive manufacturers for environmental reasons. Furthermore, German laid-open document DE 102 29 752 A1 discloses reinforcing the bottom plate of the cargo area with a partition plate which, in turn, is inserted into the spare-tire well of the bottom plate of the cargo area perpendicular to the longitudinal axis thereof and which is welded to it.
Japanese specifications JP 63043874 A, JP 11208520 A and German laid-open document DE 103 61 045 A1 also disclose the procedure of reinforcing car body surfaces, especially the bottom surfaces of vehicles, by means of a plurality of generally known ribs created in the bottom surfaces, which can extend as bottom ribs from horizontal sections of the bottom surface all the way to vertical or almost vertical sections of the bottom surface, for example, in the area of a center tunnel, thus forming wall ribs. In actual practice, however, it can be seen that, especially in the case of deep-drawn wells involving a great drawing depth, the material is drawn irregularly in the area where the rib makes a transition from the well bottom to the well wall, as a result of which it tends to rupture.
Moreover, it has been found in actual practice that, precisely in the case of the above-mentioned deep wells, the well wall and particularly the transition of the rib from the horizontal to the vertical section of a well have such a significant effect that, wherever there are several adjacent ribs of the above-mentioned type, the edge area of the horizontal section or of the well bottom with respect to the vertical section or with respect to the well wall has an accordion-like configuration so to speak, and can hardly provide any stiffness in said edge area, so that, in spite of said rib reinforcement, a great deal of additional reinforcement potential remains unutilized. This is where the invention described below comes in.